The Norwegian government is constantly changing their technical building requirements in order to lower energy consumptions by increasing isolation thickness. At the same time, the Asthma and Allergy Association is warning about houses that are built according to the new requirements might have negative impact on people’s health. Instead of isolating houses even more, a renewable energy system based on solar and energy storage in the ground, could cover the additional heat losses when building houses less airtight.

A Norwegian house consumes in average about 26 000 kWh every year. Approximately 16 500 kWh are consumed in heating the house and approximately 4 000 kWh in heating water (Statistisk Sentralbyrå, 2014). The main purpose of this thesis is to investigate whether it is possible to construct a system of solar collectors and energy wells to cover a household’s need for heating. How could the system be constructed and how could it work? These are the questions that are investigated in this thesis.

On a sunny day in Norway a horizontal plane receives about 1000 W/m2 of solar insulation. If the solar energy received on this plane during one year is summarized, the surface would receive between 700 and 1100 kWh/m2 (Salvesen, 2009). With the efficiency level and the solar collectors angle taken into consideration, a collector area of 72 m2 would produce approximately 30 000 kWh each year. A 72 m2 solar collector from ASV solar costs 90 000 NOK (ASV Solar, 2015).

This thesis proposes 24 wells with a depth of 35 meters and 3 inches in diameter to store the solar energy. The boreholes contain PVC collectors with an isolated center tube. The wells are grouped into high temperature wells and medium temperature wells, where the medium temperature wells would protect the high temperature wells from heat loss to the surroundings. The solid rock that is surrounding the high temperature wells would contain 1000 m3 , and the solid rock that is surrounding the medium temperature wells would contain 3500 m3 . Drilling the wells and installing collectors would cost more than 100 000 NOK (Huus-Hansen, 2015).

The piping system that connects the solar collectors with the wells consists of pipes, 3 pumps and 5 valves. This system is constructed to enable the right temperature of the circulation medium to flow into the right well. The system could produce energy even at partly clouded days. The pressure losses in the pipes are estimated to become approximately 30 meters in total when the system receives maximum insulation.

The main advantage of the system is that it can supply heating of the house even at a large energy demand. Many energy systems are having difficulties delivering enough energy when the need of heating is high for a longer period of time. The main disadvantage is that it may take as long as 5 years until the system has achieved optimal operational temperature. The long initiation phase is based on the time it will take to obtain the required temperature in the solid rock between the wells.

The systems present value is estimated to become -165 000 NOK, based on assumptions of 5% interest rate and expected lifetime of 30 years. Using this system will reduce the households CO2-emissions by more than 9 tons every year.

However, the thesis has many uncertainties. Some of the uncertainties are referring to the dimentioning of the walls of the energy wells, heat production in the solar collectors and the loss of pressure in the pipes.

Publisher

Norwegian University of Life Sciences, Ås

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